System and method for detecting impaired electric power equipment

ABSTRACT

A system and method for detecting impaired electric power equipment. An exemplary embodiment may receive electromagnetic radiation and process the resulting signal. For example, signal processing may be used to identify electromagnetic radiation having a particular pattern that is characteristic of electric power equipment. Furthermore, an embodiment may determine the time and/or location during testing. As a result, an exemplary embodiment may be useful for stationary and/or mobile testing of an electrical system.

This is a continuation-in-part of U.S. application Ser. No. 11/139,192,filed May 27, 2005, which is hereby incorporated by reference in itsentirety.

BACKGROUND AND SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention relate generally to asystem and method for identifying impaired electrical equipment. Moreparticularly, some exemplary embodiments of the present invention relateto a system and method for detecting impaired electric power equipment.Exemplary embodiments of the present invention may also be useful fortesting various other types of electrical systems. Furthermore,exemplary embodiments of the present invention may be useful forstationary and/or mobile testing of various types of electrical systems.

Power generation, distribution, transmission, and substation systems arejust some examples of electrical systems. Some other examples ofelectrical systems include radio systems, communication systems, controlsystems, industrial electrical systems, and other types of electricalcircuitry and systems. In addition, many other types of electricalsystems are known or may be developed.

Any type of electrical system may be responsible for creatingelectromagnetic radiation. Electromagnetic radiation includes radiofrequency radiation as well as other frequencies of electromagneticradiation. The underlying cause of the electromagnetic radiation maylimit or disrupt the operation of the electrical system that is emittingthe electromagnetic radiation. Moreover, electromagnetic radiation mayalso interfere with the operation of other electrical systems. In fact,many sophisticated electrical systems are becoming increasinglysensitive to the effects of electromagnetic radiation. Consequently,electromagnetic radiation may sometimes be referred to aselectromagnetic interference (EMI). A common definition of EMI is “anyelectromagnetic disturbance that interrupts, obstructs, or otherwisedegrades or limits the effective performance of electronics/electricalequipment.”

The causes of electromagnetic radiation vary. Equipment such aselectrical appliances, electronic equipment, motors, circuits, and otherelectrical systems can produce electromagnetic radiation, which can beinfluenced by the surrounding environment such as hills, trees,buildings, and other environmental factors. In addition, impairedelectrical equipment may be the cause of an increased level ofelectromagnetic radiation. Other causes are also possible. Regardless ofwhether the cause of electromagnetic radiation is intentional orinadvertent, hostile or friendly, or caused by jamming devices,malfunctioning equipment, or improper system operation, the resultingelectromagnetic radiation can have detrimental impact on the operationof electronics and other electrical systems.

A standard for defining power disturbances has been established by theInstitute of Electrical and Electronics Engineers (IEEE) in order tohelp address the problems caused by electromagnetic interference. Inparticular, the “IEEE Recommended Practice for Monitoring ElectricalPower Quality” defines electrical disturbances as interruptions, sagsand swells, long duration variations, impulse transients, oscillatorytransients, harmonic distortion, voltage fluctuations, and noise. Inaddition, the standard sets forth acceptable disturbance levels, andelectrical equipment manufacturers use EMI (e.g., radio frequencyinterference) shielding techniques in attempts to meet the standard.

There has been growth in the level of EMI shielding that is required aswell as in the number of new applications that require shielding.However, the development of new shielding technologies has not kept pacewith the development of new electrical systems. In addition,enhancements to old shielding technologies have also lagged behind thedevelopment of new electrical systems. In fact, shielding of electricalsystems from the effects of electromagnetic radiation is commonly viewedby manufacturers as adding little or no value to the electrical systems.Thus, the development of shielding has been relatively stagnant inrecent history.

Compounding this problem is the fact that EMI detection techniques havenot advanced rapidly enough in light of the development of new types ofelectrical systems. There are currently few research and developmentactivities to develop new devices to identify the causes of EMI. As aresult there are little to no quality commercial EMI diction devicesavailable. Currently commercial EMI detectors suffer from poorconstruction and lack the tolerances necessary to reliably detect andlocate EMI. Most commercial EMI detectors have a wide passband but stillemploy a shallow rolloff. Commercial EMI detectors only work with aparticular frequency and lack the variety necessary to be effective.Another problem with most commercial EMI detectors is that they aresusceptible to standing waves. This susceptibility to standing wavesinterferes with the EMI detectors ability to locate the disturbance. Asa result, EMI is an increasing problem.

Power line arcing is one example of a cause of EMI. As a result of thehigh voltage, power line arcing may be destructive, and it may indicatethat certain electrical equipment is in an impaired condition. In fact,any type of arcing may indicate that electrical equipment is in animpaired condition.

Arcing occurs when a sufficiently large potential difference developsbetween two objects. For example, a small gap between components ofenergized electrical equipment may lead to arcing, wherein an electricalcharge builds up and discharges across the gap. The cause of a gap maysimply be due to expansion and contraction or corrosion of theequipment. As a result, small gaps in the electrical equipment can bevery difficult to identify. Compounding the difficulty is the fact thatsome electrical equipment such as power lines may be located well aboveground level and energized with high voltage, making it impractical orinefficient for electrical utility personnel to visually inspect eachstructure or other elevated equipment in an attempt to locate animpaired piece of electrical equipment. Impaired equipment can still bedifficult to locate even if the equipment is located near ground level.For instance, multiple pieces of electrical equipment in a general areasuch as a room, a factory building, or even a general outside area canhinder the detection of an impaired piece of equipment. As a result, thelocation of impaired electrical equipment may be difficult to identify.

In light of the difficulty in locating impaired electrical equipment,there is a need for a system and method for detecting impairedelectrical equipment that may utilize the characteristics of the arcing.The pulse repetition rate is the rate at which arcing occurs across agap, which may be measured by the number of arcs per unit time. Thepulse repetition rate is typically proportional to the source voltageand inversely proportional to the width of the gap. Consequently, witheverything else being equal, a higher voltage results in a higher pulserepetition rate, and a wider gap results in a lower pulse repetitionrate. In addition to the pulse repetition rate, arcing has an RFfrequency characteristic. In particular, arcing results in theproduction of a radio frequency signal. In the case of EMI, the signalis typically broad spectrum such that it is detectable across a wideband of the radio frequency spectrum. Each arc produces a radiofrequency signal; therefore, as the width of the gap or the sourcevoltage changes, the resulting radio frequency signal also changes.Other factors may also affect the RF frequency. For example, with regardto a utility pole, the RF frequency may also be affected by: the heightof the utility pole; whether or not a ground wire runs along a side ofthe utility pole; the distance between the utility pole and adjacentpoles; the components (e.g., insulators, cutouts, etc.) that are mountedat the top of the utility pole; and whether the utility pole is asingle-phase or three-phase structure. Other factors may also impact theRF frequency. All of these parameters can and often do act as ‘antennatuning elements’ that affect the signal that is radiated when an arcoccurs. As a result, during any given 60 Hz cycle, for example, theremay be a family of different RF signals produced. Finally, arcing mayhave a modulation frequency. The modulation frequency of the arcing isnot dependent on the level of the source voltage or the width of a gapbetween electrical components. In this sense, the modulation frequencyis an independent characteristic of the radio frequency signal(s)produced by arcing. In other words, with regard to arcing caused by analternating current (AC) source, the modulation frequency is acharacteristic of the frequency of the source.

Exemplary embodiments of the present invention are directed to a systemand method for detecting impaired electrical equipment. An exemplaryembodiment of the present invention may receive electromagneticradiation and process the resulting signal. For example, signalprocessing in some embodiments of the present invention may be used toidentify electromagnetic radiation having a particular characteristic.Exemplary embodiments may utilize a wide and flat passband filter tocombat and eliminate the problem of standing waves. The use of a widefilter with a flat passband causes a cancellation effect among variousfrequencies within the passband when the EMI detector is not at theexact source. This results in a EMI detector that may be immune to thefalse source phenomenon that other EMI detectors experience. This allowsexemplary embodiments to locate the disruption more efficiently. To aidwith location of disruption, exemplary embodiments take readings atmultiple frequencies and use an averaging technique to guide a user tothe location. This averaging function may occur inherently as a functionof the wide filter employed. Furthermore, an exemplary embodiment of thepresent invention may also include the determination of the time and/orlocation during testing. As a result, an exemplary embodiment of thepresent invention may be useful for stationary and/or mobile testing ofan electrical system.

In addition to the novel features and advantages mentioned above, otherfeatures and advantages of the present invention will be readilyapparent from the following descriptions of the drawings and exemplaryembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an exemplary embodiment of a system fordetecting electromagnetic radiation of the present invention.

FIG. 2 is a graph of an exemplary embodiment of the modulation of awaveform.

FIG. 3 is an example of a map showing a high level of electromagneticradiation that is indicative of impaired electrical equipment.

FIG. 4 is a block diagram of a second exemplary embodiment of a systemfor detecting impaired electrical equipment of the present invention.

FIG. 5A is a first part of a schematic diagram illustrating an exemplaryembodiment of a system of the present invention for detecting impairedelectrical equipment.

FIG. 5B is a second part of a schematic diagram illustrating anexemplary embodiment of a system of the present invention for detectingimpaired electrical equipment.

FIG. 5C is a third part of a schematic diagram illustrating an exemplaryembodiment of a system of the present invention for detecting impairedelectrical equipment.

FIG. 5D is a fourth part of a schematic diagram illustrating anexemplary embodiment of a system of the present invention for detectingimpaired electrical equipment.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENT(S)

Exemplary embodiments of the present invention are directed to a systemand method for detecting impaired electric power equipment. FIG. 1illustrates one example of a system of the present invention. In FIG. 1,the system 10 is comprised of a signal detection circuit 12. Signaldetection circuit 12 may be any device that is adapted to receive radiofrequency electromagnetic radiation or radiation in another desiredfrequency range. The particular type of signal detection circuit 12 maybe selected to detect electromagnetic radiation within a desiredfrequency range. For example, the signal detection circuit 12 of anexemplary embodiment of the present invention may be adapted to detectelectromagnetic radiation in a frequency range outside of the normaloperating frequency range of the energized electrical equipment to betested. Furthermore, in some embodiments of the present invention, itmay be desirable for the signal detection circuit 12 to detectelectromagnetic radiation in a frequency range that does not overlap theoperating band of other electrical systems, if possible. For example,when testing a power system, it may be desirable to detectelectromagnetic radiation in a frequency range that does not include 60Hz and that also does not overlap the frequency ranges of otherelectrical systems such as cable television systems, telecommunicationsystems, AM broadcast signals, CB radio signals, and other extensivelypopulated frequency bands. For instance, an exemplary embodiment of thepresent invention may implement a signal detection circuit 12 that isadapted to detect electromagnetic radiation in the frequency range of2-11 MHz in order to avoid the AM broadcast and CB radio frequencybands. An example of a commercially available signal detection circuitthat is operable in the 2-11 MHz range is the Radar Engineers Model 246demodulator. Another exemplary embodiment of the present invention mayimplement a signal detection circuit 12 that is adapted to detectelectromagnetic radiation in the radio astronomy frequency range of72-76 MHz, more preferably the 73-74.6 MHz portion of the RF spectrumprimarily allocated for radio astronomy. By selecting a frequency bandthat is less populated, the present invention may facilitate thedetection of electromagnetic radiation that is emitted from impairedelectrical equipment (i.e., the possibility of confusion withelectromagnetic radiation that is not caused by impaired electricalequipment is lessened). An exemplary embodiment of the signal detectioncircuit 12 may enable an operator to select an operating range that ismost suitable for particular testing conditions. For example, anembodiment of the signal detection circuit 12 may include a switch orother selection mechanism that enables an operator to select a desiredfrequency range. For instance, one exemplary embodiment of the signaldetection circuit 12 may enable the selection of multiple differentfrequency ranges between 5 MHz and 500 MHz. As a result, an operator maybe enabled to select a frequency range that provides the best detectionresults (e.g., eliminates the most background noise). Furthermore, if itis desired to detect a particular type of impairment and the range ofelectromagnetic radiation that is emitted by that type of impairment isknown, then a signal detection circuit may be selected that is adaptedto detect electromagnetic radiation in that range. Nevertheless, itshould be recognized that some embodiments of the present invention maydetect electromagnetic radiation in any desired frequency range (e.g., aheavily populated frequency range or a frequency range that covers thenormal operating frequency range of the energized electrical equipmentto be tested). Moreover, some exemplary embodiments of the signaldetection circuit 12 may detect electromagnetic radiation outside of theradio frequency range.

The signal detection circuit 12 may be in electrical communication withan antenna 13 that is adapted to receive electromagnetic radiation. Anexemplary embodiment of the antenna 13 is not resonant within theoperating frequency range of the electrical equipment that is beingsurveyed. The antenna 13 may also not be resonant within the operatingfrequency range of the signal detection circuit 12. Such an embodimentmay enable the use of an antenna 13 of a size that is particularlysuitable for mobile use of system 10. In one exemplary embodiment, theantenna 13 may be a ¼ wave mobile antenna sized for the 2-meter amateurradio band. It should be recognized that other shorter or longerantennas are available and suitable for use in the present invention. Inaddition to size, a non-resonant antenna 13 may also provide the benefitthat the operation of the device is not dependent on whether the antennais resonant with a desired frequency range. Another possible benefit isthat a non-resonant, voltage sense antenna may lessen or eliminatevariations in antenna gain, which could complicate the analysis of theelectromagnetic signals. Nevertheless, certain embodiments of antenna 13may be resonant within either or both of the aforementioned frequencyranges. It should also be recognized that a directional antenna may alsobe used in the present invention.

The signal detection circuit 12 is adapted to produce an output thatbears a relationship to the detected electromagnetic radiation. Unlessexpressly set forth, the relationship of the output to the detectedelectromagnetic radiation is not limited. One exemplary embodiment ofthe signal detection circuit 12 may produce an analog output that isproportional to the level of detected electromagnetic radiation. Forexample, the analog output may have a proportional voltage and/orfrequency. For instance, an exemplary embodiment of signal detectioncircuit 12 that detects electromagnetic radiation in the 2-11 MHz rangemay produce an audio frequency output that is proportional to the levelof detected electromagnetic radiation. It should also be recognized thatsome exemplary embodiments of the signal detection circuit 12 mayproduce a digital output that bears a relationship to the level ofdetected electromagnetic radiation (e.g., an output that is proportionalto the modulation of detected electromagnetic radiation).

The signal detection circuit 12 may be in electrical communication withan optional filter 14. In particular, the filter 14 may be adapted toreceive the output of the signal detection circuit 12. An exemplaryembodiment of the filter 14 may be a band pass filter. For example, aband pass filter may be used to limit aliasing of an analog output ofthe signal detection circuit during subsequent conversion into a digitalsignal for further processing. One exemplary embodiment of a band passfilter is a fast roll-off filter such as a switched capacitor 8^(th)order band pass filter (e.g., MAX293) with 3 dB cutoff frequencies setto 2 kHz. Such an embodiment results in at least about 80 dB attenuationat approximately 3 kHz. Nevertheless, it should be recognized that theparticular characteristics of the filter 14 may be selected in order tosuit the output of the signal detection circuit 12 and the rate ofdigital sampling. For example, if the digital sampling rate is 7680samples per second, a band pass filter may be selected to preventaliasing of frequencies above the Nyquist frequency of 3840 Hz.

An analog-to-digital (A/D) converter 16 may be in electricalcommunication with the filter 14. In an exemplary embodiment in whichthe outputs of the signal detection circuit 12 and the optional filter14 are analog, the A/D converter may be adapted to sample the analogoutput and convert it into a digital signal. The rate of sampling may beselected to achieve accurate A/D conversion, which may take the rate oftravel into account if the system 10 is used for mobile testing. Forexample, an A/D converter 16 may sample at a rate of 7680 samples persecond (e.g., 128 samples per each 60 Hz cycle) in one exemplaryembodiment of a system 10 that is adapted for mobile testing of a powersystem (e.g., a power line).

A digital signal processing (DSP) circuit 18 is adapted to receive thedigital signal produced by A/D converter 16. Examples of a digitalsignal processing circuit 18 include, but are not limited to, the TexasInstruments TMS320 series of digital signal processors, other mixedsignal processors, and other similar or suitable processors. The digitalsignal processing circuit may be adapted to receive digital signals andidentify a modulation component associated with spiking and having afrequency component within a predetermined frequency band. An exemplaryembodiment of the digital signal processing circuit 18 may function as adigital filter. Examples of digital filters include infinite impulseresponse filters (IIRs) and finite impulse response filters (FIRs). Anexemplary embodiment of a finite impulse response filter may implement aFourier transform (e.g., a fast Fourier transform or a discrete Fouriertransform) to identify a particular component of the digital signal. Forexample, a discrete Fourier transform may be used to identify acomponent of the digital signal having a modulation frequency within apredetermined band and frequency.

A power system in the United States typically operates at 60 Hz. As aresult, there is a peak in the voltage signal every half cycle. In thecase in which there is impaired equipment in a power system, arcingcommonly occurs when the voltage signal approaches its positive andnegative peaks. In other words, a charge may build up and jump across animpaired area one or more times approximately around each peak of thevoltage signal. The number of arcs per unit time is the pulse repetitionrate. The beginning and end of the arcing around each peak is a functionof factors such as the voltage and the size of the gap. Moreover, thefrequency of the discharge signal (i.e., the RF frequency) typicallyvaries based on the particular characteristics of the impairedequipment. Nevertheless, a modulation frequency of the electromagneticradiation caused by the arcing is approximately 120 Hz since the arcingoccurs around every positive and negative peak of the voltage signal.FIG. 2 shows an example of a waveform having 120 Hz modulation. Thus,when testing an electrical system that operates at 60 Hz, the digitalsignal processing circuit may be used to identify and isolate acomponent of the electromagnetic radiation that has a modulationfrequency of approximately 120 Hz. For example, the digital signalprocessing circuit may identify a component having a modulationfrequency in a predetermined band that includes 120 Hz modulation (e.g.,115-125 Hz). Of course, if testing electrical equipment that operates ata frequency other than 60 Hz, the same principles may still apply. Forexample, a modulation frequency of arcing on the 50 Hz power grid inEurope is 100 Hz. In other words, the primary modulation frequency ofthe arcing is the second harmonic frequency of the fundamental frequencyof the transmitted signal (i.e., the fundamental frequency of the signalsource). In light of these characteristics of arcing, an exemplaryembodiment of the digital signal processing circuit 18 may be used toidentify a signal component having the primary modulation frequency(e.g., 120 Hz in the United States or 100 Hz in Europe). In fact, itshould be noted that a 60 Hz modulation component may also besignificant in the United States, and it should be recognized that a 50Hz modulation component may also be significant in Europe. As a result,an exemplary embodiment of the digital signal processing circuit 18 maybe used to identify a component having a modulation frequency that isequivalent to the fundamental frequency of the signal source (e.g., 60Hz in the United States or 50 Hz in Europe) or any of the harmonicsthereof for the purpose of identifying arcing caused by a power system.Thus, in the United States for example, harmonics above 120 Hz may alsobe useful. Although we have discussed the invention primarily withregard to the power systems in the United States and Europe, it shouldbe recognized that the same principles are applicable to other types ofpower systems that have different fundamental frequencies.

Some exemplary embodiments of the digital signal processing circuit 18may also perform other functions. For example, the digital signalprocessing circuit may be adapted to determine the mean value (RMS) andpeak value of the electromagnetic radiation in real time. The digitalsignal processing circuit may also be adapted to determine the standarddeviation and level of background noise in real time. Alternatively, apredetermined background level may be provided to the digital signalprocessing circuit. Such information can be used to improve the accuracyof locating impaired equipment. However, it should be recognized thatsuch calculations may be made later using stored data in some otherembodiments of the present invention.

Some exemplary embodiments of the digital signal processing circuit 18may be dynamically changed to adjust to specific survey conditions. As aresult, a different unit may not be required for each different type oftest. For example, hardware may not have to be replaced in order toadjust to specific testing conditions.

A location tracking circuit 20 may be included in the system 10. Thelocation tracking circuit 20 may be any device that is adapted toreceive data regarding the location of system 10. An example of alocation tracking circuit 20 is a global positioning system (GPS)circuit that may be adapted to automatically track the location of thesystem 10 by recording geographic coordinates. The refresh rate of theGPS circuit may be selected to achieve the desired accuracy, which maytake the rate of travel of system 10 into account. For example, anexemplary embodiment of a GPS circuit may take a measurement once everysecond. In such an embodiment, if the system 10 travels in a vehiclemoving at 60 miles per hour, the GPS circuit would take a measurementevery 88 feet. Another exemplary embodiment of a GPS circuit may take100 measurements every second. A different operating mode may be to onlytake a measurement when the level of detected electromagnetic radiationexceeds a predetermined value. It should also be recognized that a GPScircuit may also be adapted to automatically determine the time in someexemplary embodiments of the present invention. Exemplary embodiments ofGPS circuits include, but are not limited to, the Motorola M12+ TIMINGONCORE RECEIVER and other similar or suitable GPS circuits.

A computing device 22 may be in electrical communication with thedigital signal processing circuit 18 and the location tracking circuit20. The computing device 22 may be any device that is adapted tocorrelate the output (e.g., the component signal having predeterminedmodulation, the peak value, the mean value, the standard deviation,and/or the background noise level) of the digital signal processingcircuit 18 with the location data provided by the location trackingcircuit 20. Examples of computing devices include, but are not limitedto, microprocessors and microcontrollers. As a result, the computingdevice 22 may be adapted to identify or determine the level of aparticular component of electromagnetic radiation at a particularlocation. Thus, if the level of a particular component ofelectromagnetic radiation is relatively or uncharacteristically high ina particular location without a legitimate reason, a location ofimpaired electric power equipment may have been detected. Moreover, someexemplary embodiments of the computing device 22 may be adapted toidentify the particular type of impaired equipment. For example, someembodiments of the computing device 22 may be programmed to identify theparticular type of impaired equipment based on the frequency and/orvoltage and/or modulation characteristics of the detectedelectromagnetic radiation. For instance, if it is known that a crackedinsulator emits electromagnetic radiation having a particular frequencyand/or voltage and/or modulation, the computing device 22 may beprogrammed to identify that measurement as indicative of a crackedinsulator. The same type of process could also be performed for any typeof electrical component including, but not limited to, arresters,insulators, cutouts, utility pole hardware, and other types ofelectrical components. In addition, some exemplary embodiments of thecomputing device 22 may be adapted to compare the mean value and peakvalue of the electromagnetic radiation to the level of background noiseusing data provided by digital signal processing circuit 18. Thecomputing device 22 may use this data to determine if the backgroundnoise is causing a false indication of impaired equipment. In otherwords, the computing device 22 may use this data to determine if thebackground noise is causing a false indication that there is arelatively or uncharacteristically high level of electromagneticradiation. One exemplary embodiment of the computing device 22 maycompare this data in decibels (dB).

In FIG. 1, analog-to-digital converter 16, digital signal processingcircuit 18, and computing device 22 are shown as separate devices tomore clearly show the invention. Nevertheless, it should be recognizedthat the computing device 22 may be comprised of an analog-to-digitalconverter 16 and a digital signal processing circuit 18 in exemplaryembodiments of the present invention. In other words, analog-to-digitalconverter 16, digital signal processing circuit 18, and computing device22 may be embodied in a single device or in multiple devices in thepresent invention. The digital signal processing circuit may be adaptedto receive digital signals and identify a modulation componentassociated with spiking and having a frequency component within apredetermined frequency band.

The system 10 may also include an optional memory device 24. Examples ofmemory devices include, but are not limited to, multimedia cards (MMCs)(e.g., a 64 MB MMC), compact flash cards, secure digital cards, PROM,EPROM, EEPROM, and other similar or suitable types of memory. The memorydevice 24 may be in electrical communication with the computing device22. For example, the memory device 24 may be in serial or parallelcommunication with the computing device 22. In one exemplary embodiment,the system 10 may include a socket for receiving memory device 24. Forexample, a MMC may include a backing with a thumb hole to enable it tobe easily removed from the socket. Alternatively, an exemplaryembodiment of memory device 24 may have a wired or wireless connectionto system 10. For instance, there may be a radio link or other type ofcommunication link between computing device 22 and memory device 24(e.g., memory device 24 may be located at a remote base station) tofacilitate the storage of data. In an exemplary embodiment, the memorydevice 24 may be adapted to store the data concerning the output of thedigital signal processing circuit 18, the time, and the location dataprovided by the location tracking circuit 20. As a result, the memorydevice 24 may be particularly useful for mobile testing by system 10.For example, the memory device 24 may automatically record data as thesystem 10 is continuously or intermittently moved during a survey ofelectrical equipment. For instance, one exemplary embodiment of thememory device 24 may record data about once every second during oneexemplary mode of operation. As a result, a skilled technician is notrequired to analyze the data as it is being determined by the system.Instead, the data may be recorded during routine field work such asrevenue meter reading, for example. At a later time, the stored data maybe retrieved and analyzed (e.g., using a map) to determine if there isimpaired equipment somewhere out in the field.

The system 10 may include a mode in which an exemplary embodiment of thememory device 24 may be controlled to capture a waveform ofelectromagnetic radiation in addition to the other data. For example,the memory device 24 may be adapted to capture a waveform of theelectromagnetic radiation modulation when there is a transition from alow level signal to a high level signal. In other words, there may be ananalog input from the signal detection circuit 12 to the computingdevice 22, which may initiate the storage of the waveform on the memorydevice 24. This enables an operator to play the waveform back and listento it. By listening to the audio signature, an operator may be able toidentify the source of the electromagnetic radiation because each typeof impairment may have a characteristic audio signature. For example, awaveform capture of about 1 to 2 seconds or longer may enable anoperator to identify the type of impairment. In the meantime, anexemplary embodiment of the memory device 24 may be programmed to notcapture another waveform until the system 10 has traveled at least 200feet or another desired distance from the position of the previouswaveform capture. Thus, if the vehicle is stopped, such an embodiment ofthe memory device 24 may not make another waveform capture until thevehicle is 200 feet or another desired distance away from the locationof the previous waveform capture. In such an embodiment, driving in acircle would not necessarily move the vehicle the desired distance awayfrom the location of the previous waveform capture; therefore, memorydevice 24 may also be set to capture a waveform based on a desired timeinterval (e.g., every 10 minutes). Such a setup may be particularlyuseful in stationary or cable vault applications of the presentinvention, for example.

The operation of an exemplary embodiment of the memory device 24 willnow be described. An exemplary embodiment of the memory device 24 mayautomatically record time, location, and signal strength data in oneblock or portion of memory. For example, signal strength data mayinclude the amount of 120 Hz modulation (e.g., the mean and/or peak) forabout each second or another desired time interval in an exemplaryembodiment of the present invention. As discussed below, an exemplaryembodiment of a mapping and analysis program may be used to create a mapusing the location data and the 120 Hz modulation peak data from thisblock or portion of memory. Another block or portion of the memory mayautomatically record time and waveform data. As previously mentioned,the waveform data may be used to look with more detail at a particularlocation. An exemplary embodiment of a mapping and analysis program mayread both blocks of memory and match up the data by looking for datawith a common time stamp. As a result, the waveform data may be used tolook with more detail at a particular impairment. Such an embodiment ofthe memory device 24 may be particularly useful for the purposes of thepresent invention. Nevertheless, it should be recognized that certainembodiments may utilize more or less data and may store and access it ina different way in order to detect impaired electrical equipmentutilizing the principles of the present invention.

As mentioned above, an optional mapping (and/or analysis) program 26 mayalso be included in the system 10. The mapping program 26 may be anintegral or remote component of the system 10. For example, the mappingprogram 26 may have a wired or wireless connection to the system 10. Foranother example, the mapping program 26 may be adapted to receive thedata from memory device 24 without the benefit of a wired or wirelessconnection to the system 10, such as by receiving a memory card.Regardless of the particular type of system architecture, the mappingprogram 26 may receive the data produced by computing device 22. Themapping program 26 may then produce a map that illustrates the level ofelectromagnetic signal strength at predetermined locations. Forinstance, the mapping program 26 may produce a map showing the levels ofa particular component of electromagnetic radiation that is generated byelectrical equipment along a surveyed route. FIG. 3 is an example of amap that shows a high level of electromagnetic radiation caused by apower line as observed by an exemplary device of the present inventionmounted in an inspection helicopter.

An exemplary embodiment of system 10 may be used to test a variety ofelectrical systems. For example, an exemplary embodiment of the system10 may be used to survey a power system including, but not limited to,at least one power line along a particular route. For instance, thesignal detection circuit 12 and the location tracking circuit 20 may beprovided in a vehicle. An antenna for the signal detection circuit 12may also be provided in the vehicle. In other words, circuits 10 and 12and the antenna may be provided anywhere in the interior or exterior ofthe vehicle. Examples of a vehicle include, but are not limited to,automobiles (e.g., cars, trucks, and vans), trains, airplanes,helicopters, boats, and any other type of mechanized equipment that maybe used to transport something. The vehicle may travel in a path in thevicinity of the electrical equipment. The distance from the electricalequipment may be any suitable distance. A suitable distance may be afunction of the sensitivity of the signal detection circuit and thelocation of the equipment being tested in relation to other sources ofelectromagnetic radiation. In one exemplary embodiment of the presentinvention, the vehicle may be anywhere within 200 feet of the electricalequipment. In other embodiments of the present invention, the vehiclemay be further than 200 feet from the electrical equipment. While thevehicle is moving in the path of the electrical equipment, the system 10may simultaneously detect electromagnetic radiation and receive locationdata. A digital signal may be derived from the detected electromagneticradiation such as previously described. Furthermore, a digital signalprocessing circuit 18 may be provided in the vehicle for processing thedigital signal and identifying a component associated with spiking andhaving a modulation frequency within a predetermined band. Thereafter, acomputing device 22 may be used to control the creation of a map or anyother type of graphical or textual representation of the component andthe location data. These functions may all occur while the vehicle ismoving in the vicinity of the electrical equipment or at a later time.For example, these functions may be automatically performed while anelectrical worker is simply riding in the vehicle in the normal courseof his or her job. As another example, the data (e.g., time, longitude,latitude, the level of detected electromagnetic radiation, and/or otherdata) may be automatically stored for subsequent use in some exemplaryembodiments of the invention. If the mapping program is not provided inthe vehicle, a map may be created at a later time using the stored data.For example, a map may be created to show the levels of electromagneticradiation produced by the electrical equipment (e.g., a power line) thatwas surveyed.

FIG. 4 illustrates another exemplary system of the present invention. Inthis example, the system 30 is also comprised of a signal detectioncircuit 32, an optional antenna 33, a filter 34, an A/D converter 36, adigital signal processing circuit 38, a computing device 42, and anoptional memory device 44. With regard to these components, theoperation of system 30 may be similar to the operation of system 10. Thedigital signal processing circuit may be adapted to receive digitalsignals and identify a modulation component associated with spiking andhaving a frequency component within a predetermined frequency band.However, the system 30 includes a timing circuit 40. Timing circuit 40may be any type of device that is adapted to determine time data. Aspreviously mentioned, a GPS circuit is one example of a timing circuit40. An internal clock is another example of a timing circuit 40. Thesystem 30 may simultaneously determine the time data while detecting theelectromagnetic radiation in an exemplary embodiment of the invention.The Motorola M12+ TIMING ONCORE RECEIVER is an example of timing circuitthat provides a high degree of accuracy (e.g., 10 ns) which may bedesirable for an exemplary embodiment of system 30 that requires precisetiming. Computing device 42 is in electrical communication with digitalsignal processing circuit 38 and timing circuit 40. In this exemplaryembodiment, the computing device 42 is adapted to correlate the outputof digital signal processing circuit 38 with the time data provided bytiming circuit 40. Furthermore, an exemplary embodiment of the computingdevice 42 may be adapted to use angle of arrival calculations to furtheridentify the location of impaired equipment. The optional memory device44 may be used to store data related to the output of digital signalprocessing circuit 38 and time data provided by timing circuit 40.

The system 30 may also include an optional operational record 46.Operational record 46 may be any electronic or hard copy (e.g., paper)record that correlates the operation of electrical equipment with timedata. For example, the operational record 46 may be a static record thatdoes not require updating (e.g., if the electrical equipment alwaysperforms the same operation at the same time) or a fluid record thatrequires updating (e.g., automatic updating) to reflect the operationalstatus of the electrical equipment. One example of an operational record46 is a sequence of events log. The time data may be provided by timingcircuit 40 or another source. If operational record 46 is in electronicform, the operational record may be provided to computing device 42 inorder to correlate the operation of electrical equipment with the outputof digital signal processing circuit 38. Furthermore, the operationalrecord 46 may be stored in memory 44 for subsequent analysis. On theother hand, if the operational record 46 is a hard copy, a systemoperator may visually compare the operational record 46 with the datadetermined by computing device 42. In any of these cases, impairedelectrical equipment may be detected by checking the status of eachpiece of electrical equipment at the time of a relatively oruncharacteristically high level of electromagnetic radiation. In lightof these features, the system 30 may be particularly useful forstationary testing of electrical equipment. Nevertheless, it should berecognized that system 30 may also be useful for other types of testingincluding, but not limited to, testing that involves limited movement.

Another exemplary embodiment of the present invention may combine thefeatures of system 10 and system 30. In particular, this exemplaryembodiment may include a location tracking circuit as well as a timingcircuit. In addition, this exemplary embodiment may also include anoperational record. As a result, this exemplary embodiment of theinvention may be particularly well suited for stationary and mobiletesting.

FIGS. 5A-5D illustrate another exemplary embodiment of a detectioncircuit 50. This exemplary embodiment may provide improved detection ofimpaired equipment such as by substantially eliminating or limitingfalse sources. In this example, circuit 50 may include an antenna 52that may be in electrical communication with at least one diode 54(e.g., a pair of diodes as shown in this embodiment). In someembodiments, the antenna 52 may be tuned to about 144 MHz. In someembodiments, the antenna is in range of a broadband signal. The antennamay be a two part antenna using high frequency. In other embodiments, afrequency of about 100 MHz may be used to decrease the problem ofcorona-induced emissions. As used herein, electrical communication shallnot be limited to a direct electrical connection; intermediatecomponents may be provided between the items that are in electricalcommunication. If multiple diodes 54 are provided, the diodes 54 may beconnected in series such as in this example. In one exemplaryembodiment, diode(s) 54 may serve to protect the circuit from damagethat could be caused by a power distribution line. Circuit 50 may alsoinclude a filter 56 in electrical communication with antenna 52. Thefilter 56 may have a flat response and a wide passband. In someexemplary embodiments the passband may have a width of about 10 MHz,although it should be recognized that passband may be wider. The filter56 may also have a steep 20 dB roll off per decade. In this example,filter 56 is an analog 8^(th) order band pass filter comprisinginductor-capacitor pairs. In other embodiments, the filter 56 may be aceramic filter, saw filter, crystal filter, inductor-capacitor filter,or any other suitable filter. One desirable characteristic of such anexemplary filter arrangement is steep cut-out of signal outside thefrequency band of interest, which advantageously suppresses unwantednuisance signals and/or noise. The use of a steep cut-off provides theEMI detector the ability to reject nearby intentional radiotransmitters. Other exemplary embodiments may include a different orderfilter suitable for a particular application. In one embodiment, theanalog filter is adapted to pass signals having frequencies in the rangeof about 130 MHz to about 170 MHz and more preferably in the range ofabout 145 MHz to about 155 MHz (e.g., about 147 MHz). Such frequencyranges may be outside of corona-induced electrical emissions and hencehelp to reduce the detection of corona-induced emission noise. At leastone amplifier stage 58 may be in electrical communication with filter56. In this example, there are two stages of amplification 58, eachproviding about 20 dB gain (i.e., 40 dB gain total). The at least oneamplifier stage may comprise RF amplifier(s). At least one switch 60(e.g., a wideband analog switch) may be in electrical communication withamplifier stage(s) 58. In this exemplary embodiment, two switches 60 areprovided for high isolation and low insertion loss. A variable gainamplifier 62 may be in electrical communication with switch(es) 60,wherein variable gain amplifier 62 may be adapted to provide linear gaincontrol. More particularly, this exemplary embodiment may provideapproximately 0 to 45 dB range (e.g., −10 dB to 30 dB). In otherexemplary embodiments, a pair of switches 60 may be used. The switchpair may be IF switch ICS. Multiple paths may be located between thepair of switches. The first path may be 20 dB attenuated and the secondpath may be a straight path. In this manner, it allows for pathselection. In other embodiments there may be no attenuation for highersignals wherein at least one switch is SWI. A potentiometer 64 may beprovided for controlling the gain of variable gain amplifier 62. In oneexemplary embodiment, the potentiometer may be provided on an enclosurefor circuit 50 for easy access and adjustability. The variable gainamplifier 62 may be wired to the potentiometer 64 to allow adjustment ofthe RF signals. A switching diode 66 may be in electrical communicationwith variable gain amplifier 62 for switching in response to a suitablesignal. A diode detector circuit may also be included. The diodedetector circuit may sum the amounts of the RF energies. The switchingdiode 66 may be adapted to control an audio amplification stage 68 inorder to indicate detection of a source of electromagnetic radiationhaving the desired characteristics. Optionally, a visible indicationsuch as an LED or any other type of light may be provided to indicatedetection of a source of electromagnetic radiation having the desiredcharacteristics. In other embodiments, a wireless transmitter may beused in conjunction with the detection circuit 50. A receiver may alsobe used and attached to the user's person, such as attached to a belt.The wireless transmitter may send a signal to the receiver and thereceiver may store the information for later retrieval.

Exemplary embodiments of the present invention may also include otherfeatures. For example, an analog or digital squelch filter may beprovided before, by, or after the digital signal processing circuit. Anexemplary embodiment of a squelch filter may be provided by the digitalsignal processing circuit and may be used to filter out background noiseand/or low level signals that are not indicative of impaired electricalequipment. Such an embodiment may be particularly useful if there is anaudible signal that indicates the level of electromagnetic radiation.For instance, an exemplary embodiment of the EMI device as describedherein may be used in tandem with other detection techniques such asacoustics to create a more comprehensive equipment health monitor. Oneexample is a generator step up (GSU) equipment health monitor whereinthe EMI device may be combined with an acoustics system and/or anothersuitable system for monitoring dissolved, combustible gases (e.g.,Hydran for H₂) in order to more comprehensively monitor the status ofthe transformer equipment. Furthermore, for underground, stationaryapplications of the present invention, it should be recognized that aGPS circuit or other circuitry of the present invention may optionallybe located in a manhole cover or in another suitable location in orderto facilitate signal reception.

An exemplary embodiment of the system of the present invention may alsoinclude a hand-held testing unit (e.g., a hotstick). For example, asignal detection circuit may be provided in a hand-held unit tofacilitate up close testing of a particular location. Such a circuit maybe the only signal detection circuit, or there may be multiple signaldetection circuits. If desired, a switch or other selection mechanismmay be provided to select between multiple signal detection circuits.

For another example, the digital signal processing circuit and/or thecomputing device may be in electrical communication with a speaker. Inother words, an exemplary embodiment of the present invention mayproduce an audible sound that varies with the level and/or frequency ofthe detected electromagnetic radiation. Similarly, an exemplaryembodiment of the present invention may provide a visual indicator thatis indicative of the level of detected electromagnetic radiation. Forexample, the digital signal processing circuit and/or the computingdevice may be in electrical communication with an LED or LEDs that turnon or change colors based on the level of detected electromagneticradiation. In one exemplary embodiment of the present invention, a 0.125inch phone jack may be used to place an LED in electrical communicationwith the system (e.g., the computing device). The LED may be placed inview of an operator of the system (e.g., a vehicle operator) to providea real time indication of the level of electromagnetic radiation. Forexample, the LED may be a multi-color LED, wherein each color representsa different status of the system. Exemplary embodiments of the presentinvention may also include other types of visual displays including, butnot limited to, graphic displays and text displays. For example, visualdisplays may be in communication with the computing device.

It should be recognized that a system of the present invention may beprovided as a single unit or as multiple units. Furthermore, exemplaryembodiments of the present invention may operate on batteries, byconnection to an electrical outlet, or both. For example, one embodimentof a system of the present invention may be powered by a vehicle batteryor another type of battery. A vehicle electrical system is anotherexample of a suitable power source. It should also be recognized thatpower may be provided by inductive pickup from the equipment (e.g., apower line) to be monitored. For example, inductive power may beparticularly useful in underground applications of the present inventionsuch as cable vault monitoring.

EXAMPLES

One exemplary embodiment of a system of the present invention is aversatile tool for identifying the source of electromagneticinterference that may be used in different ways such as described below:

-   -   1. In one example, a system may be used to evaluate a utility        pole from the ground. For instance, when patrolling for EMI, the        results may not clearly point to a single pole. In this case, an        exemplary embodiment of a system may help to determine which        pole(s) actually contain EMI sources.    -   2. Use an EMI patrolling method (such as an exemplary system of        the present invention that is transported by a vehicle) to find        the general location of the strongest EMI level for a given        area.    -   3. Begin by setting the exemplary system's attenuation switch to        0 db and gain control to 10. Approach the pole nearest to the        maximum signal location identified in step 1.    -   4. Position the antenna of the exemplary system against the wood        of the pole or against the pole ground. If a strong signal is        detected, turn down the gain control until the sound produced is        relatively quiet. The attenuation switch may be set to −20 dB        for extremely strong situations.    -   5. Take the exemplary system to the next closest pole and        perform a similar measurement. If the sound is stronger at this        pole, turn the gain control down farther in order to achieve a        sound level similar to that of step 3.    -   6. Repeat this process for all poles in the area that seem        likely EMI sources based on the initial patrol. Do not turn the        gain control up during the locating process.    -   7. The pole with the strongest signal is the best place to start        inspecting hardware. If several poles show very similar        readings, it may be likely that such poles are EMI sources.

In other exemplary embodiments, the process of performing a transmissionline EMI survey may include a large number of measurements of EMI signalstrengths are collected. The EMI signal strengths may be collected asonce-per-second intensities and as time-domain waveforms. Criteria maybe established to estimate the criticality of a located EMI source.Criticality is intended here to be a measure of the need to identify andcorrect the offending equipment in a timely manner. An example of thisprocess is described below.

-   -   1. A one second signal level (peak 120 Hz component) must be        high enough to trigger a waveform capture.    -   2. The detected signal level must demonstrate increasing        intensity as the EMI source is approached, a maximum intensity        must be achieved and decreasing intensity after passing the EMI        source.    -   3. Based on the AEP TGIS, a transmission facility must be in        close proximity (approximately 100 feet) to the indicated EMI        source. This transmission facility may be a transmission tower,        the conductor span between two towers, or a transmission        substation.    -   4. If the site is approached on more than one or more vehicle        pass, a high intensity signal must be present for more than 50%        of the passes. In other exemplary embodiments, a high intensity        signal may be present in at least one pass.    -   5. A steady, periodic pattern in a captured waveform indicates a        less critical situation than an unstable, aperiodic signal.

Once a pole has been identified as a source of EMI, the exact piece ofequipment causing the noise may be determined by the use of an exemplaryembodiment of a system of the present invention on a hotstick.

-   -   1. Begin by setting the exemplary system's attenuation switch to        9 db and gain control to 10. Approach the hardware on the pole        inspecting one item at a time. If a strong signal is detected,        turn down the gain control until the sound produced is        relatively quiet. The attenuation switch may be set to −20 dB        for extremely strong situations.    -   2. Use the exemplary system to inspect each piece of equipment        and each splice individually. Remember that EMI can be carried        across conducting objects and can form standing wave patterns.        Also, be aware that undamaged lightning arrestors can show high        readings when there are other sources of EMI nearby.    -   3. Focus on the strongest sources of EMI first. There may be a        chance that weaker “sources” may actually be standing wave        reflections caused by the actual source.    -   4. If the exemplary system points to a connection, attempt to        tighten or re-press the connection. If it points to an        insulating device such as a pin insulator, cutout, dead end,        etc., use a leakage current tester to verify if the insulator is        leaking current. Replace any insulator that is leaking        significant amounts of current.    -   5. If a lightning arrestor is found to be the strongest or only        source, the lightning arrestor may be replaced. Check the new        arrestor for EMI after installing. If the new arrestor also        shows high levels of EMI, the real source of EMI may not have        been found. It is possible that the actual source is on a nearby        pole instead of the one being worked on.

It should be understood that other methods of use of an exemplary systemof the present invention may be possible. Furthermore, the settingsdiscussed in the aforementioned examples are only for purposes ofexample. Other variables are also possible.

Any embodiment of the present invention may include any of the optionalor preferred features of the other embodiments of the present invention.The exemplary embodiments herein disclosed are not intended to beexhaustive or to unnecessarily limit the scope of the invention. Theexemplary embodiments were chosen and described in order to explain theprinciples of the present invention so that others skilled in the artmay practice the invention. Having shown and described exemplaryembodiments of the present invention, those skilled in the art willrealize that many variations and modifications may be made to affect thedescribed invention. Many of those variations and modifications willprovide the same result and fall within the spirit of the claimedinvention. It is the intention, therefore, to limit the invention onlyas indicated by the scope of the claims.

What is claimed is:
 1. A system for detecting impaired electric powerequipment that produces an increased level of electromagnetic radiation,said system comprising: a signal detection circuit adapted to produce ananalog output that is proportional to a level of electromagneticradiation; a band pass filter adapted to receive said analog output ofsaid signal detection circuit comprising an 8^(th)-order filter furthercomprising inductor-capacitor pairs embodying frequency cut-offcharacteristics to pass signals having frequencies in the range of about130 MHz and 170 MHz and more preferably in the range of about 145 MHzand 155 MHz; an analog-to-digital converter in electrical communicationwith said band pass filter, said analog-to-digital converter adapted toconvert an output of said band pass filter into a digital signal; adigital signal processing circuit adapted to receive said digital signalfrom said analog-to-digital converter and identify a modulationcomponent associated with spiking and having a frequency componentwithin a predetermined frequency band; a location tracking circuitadapted to receive location data; a timing circuit adapted to determinetime data; a computing device in electrical communication with saidtiming circuit, said location tracking circuit, and said digital signalprocessing circuit, said computing device adapted to process data fromsaid modulation component and said location data; a memory device inelectrical communication with said computing device, said memory deviceadapted to store said data related to said modulation component and saidlocation data; and a mapping program adapted to produce a map derivedfrom said data from said modulation component and said location datawherein said mapping program is adapted to show the levels ofelectromagnetic radiation relative to said location data.
 2. The systemof claim 1 further comprising: an antenna in communication with saidsignal detection circuit; and wherein said antenna is adapted to receiveelectromagnetic radiation.
 3. The system of claim 2 wherein said antennais not resonant within the operating frequency range of electric powerequipment that said system is adapted to survey.
 4. The system of claim2 wherein said antenna is resonant within the operating frequency rangeof electric power equipment that said system is adapted to survey. 5.The system of claim 2 wherein said antenna is a directional antenna. 6.The system of claim 1 wherein said analog output is adapted to be avoltage proportional to a time-varying level of electromagneticradiation detected by said signal detection circuit in a predeterminedfrequency range.
 7. The system of claim 1 wherein said signal detectioncircuit is adapted to detect electromagnetic radiation in a frequencyrange of about 2-11 MHz.
 8. The system of claim 1 wherein said locationtracking circuit and said timing circuit are provided by a globalpositioning system (GPS) circuit.
 9. The system of claim 1 wherein saidband pass filter is adapted to limit aliasing during conversion of saidoutput of said band pass filter into said digital signal.
 10. The systemof claim 1 wherein said predetermined frequency band is inclusive of 120Hz modulation.
 11. The system of claim 1 wherein said predeterminedfrequency band is inclusive of a fundamental frequency of a source ofelectromagnetic radiation.
 12. The system of claim 1 wherein saidpredetermined frequency band is inclusive of a second harmonic frequencyof a source of electromagnetic radiation.
 13. The system of claim 1wherein said computing device is a microcontroller.